Our overall objectives are to understand the genetic regulatory mechanisms responsible for three related phenomena: coordinated gene expression within individual cell types, functionally important evolutionary changes among species and certain of those human diseases for which structurally aberrant proteins have yet to be found. Our premises are: 1) there must be genomic hallmarks which account for the characteristic array and relative abundance of proteins characterizing specific cell types and the differences between species; 2) these hallmarks involve genomic elements other than those encoding proteins. To search for such genomic elements, we propose to examine the DNA organization of two human chromosomes, the X and Y, which have profound effects on differentiation and development. Our aims are: one. to generate a high density, DNA-based physical map of the human X and Y chromosome using recombinant DNA techniques; two, to investigate the molecular organization of these two chromosomes and the organization of homologous autosomal segments; three, we will utilize overlapping and homologous clones, restriction enzyme mapping, cot analyses and DNA sequencing to investigate the functional activity of specific sets of sequences through transcriptional and DNA modification analyses, with particular emphasis on X chromosome inactivation; four, to examine the evolutionary history and topographic mobility of particular classes of DNA within each chromosome; and five, to associate specific DNA probes with specific disorders or chromosomal function through restriction length polymorphisms. Our studies should provide insight into the chromosomal and genomic organization of specific sets of DNA sequences associated with chromosomes of functional importance, contribute to an understanding of the relationship between chromosome structure and function, reveal the evolutionary history of these two chromosomes and help elucidate the molecular mechanisms responsible for X chromosome inactivation.